The present invention relates generally to a packing container blank. More specifically, the present invention relates to a packing container blank having two straight, parallel lateral edges and two notches transverse edges. The invention also relates to a method for the manufacture of the packing container blank and a packing container made from the blank.
Packing containers for the packing of liquid foodstuffs exist in a number of different types. One of the more usual is the so-called gable-top type which is in the main of parallelepipedic shape, but has a ridgelike top with a traverse sealing fin directed upwards. At present the same type of package also exists with the fin folded down and a substantially plane top. The packing container is manufactured from a flexible laminate which includes a carrier layer of paper and external liquid-tight plastic layers including possible further layer of e.g. aluminum foil. The laminated material is fed in the form of individual blanks to the packing machine where the packing containers are formed, filled and sealed. The blanks have previously been folded and sealed so that they obtain a tubular shape of substantially square cross-section. Stacks of such shaped blanks in flattened condition are supplied to the packing machine which subsequently raises them to tubular shape and provides them with bases. During successive transfer through the packing machine the blanks are filled with contents, e.g. milk, whereupon they are closed in that the top is formed and sealed.
The blanks from which the packing containers are manufactured are constituted of material sheets which have been detached from a continuous web of packing material and have been given an outer contour which is adapted to the size and shape when the finished packing container is intended to have. For the type of packing container described, that is to say gable-top packages, the sheet is given a substantially four-sided main shape, with only two of the lateral edges of the sheet, however, being straight. The two other opposite edges have an uneven edge line with projecting portions of material, which in the subsequent conversion of the sheet to a finished packing container are intended to form the sealing fin directed upwards, and overlapping sealing lugs at the bottom of the packing container. These non-uniform edges are a great and serious disadvantage, since owing to their irregularity they make impossible a rational cutting out of the blanks edge-in-edge with each other, and cause an appreciable amount of waste material. This not only brings about increased material costs but also renders the manufacture extremely difficult, since the wastage in the form of individual small bits of material constantly has to be removed and taken care of, so as not to disturb the production.
Various attempts have been made in the past to solve this problem by making the edges more uniform or reducing in some other manner the wastage on punching out the blanks. However, no acceptable solution has been suggested, and this is probably due to the fact that not only has the cutting out to be facilitated, but the blanks must also be provided with edges permitting the manufacture of packing containers without increased risk of leakage at the top or bottom. Thus it was necessary to avoid designing the blanks in such a way that the area of the available sealing surfaces, which are used for the sealing of the packing container, would be reduced.
It is an object of the present invention to provide a packing container blank of such a shape that the abovementioned disadvantages are avoided.
It is a further object of the present invention to provide a packing container blank on which opposite edges are formed according to a repeatable identical pattern, so that the blanks can be punched out in continuous manufacture from a web without waste material being produced.
It is a yet further object of the present invention to provide a packing container blank of such a shape that the surfaces, which during the conversion of the blank to a packing container are to be used for sealing of the material, are given maximum size and optimum shape.
These and other objects have been achieved in accordance with the invention in that a packing container blank having two straight parallel, lateral edges and two transverse edges is given the characteristic that the transverse edges are indented or notched according to a pattern which is repeated over the width of the blank.
Preferred embodiments of the packing container blank in accordance with the invention have been given, moreover, the characteristics which are evident from the description below.
By giving the transverse edges of the packing container blank a notched pattern which is repeated over the width of the blank the possibility is provided of cutting the blanks during continuous manufacture through punching the same from a web in such a manner that waste material can be wholly avoided. Since, thanks to the design of the blank in accordance with the invention, the notched, transverse edges on two blanks adjoining each other can now be cut by a common cut, similarly to the two straight, parallel lateral edges, the creation of waste material, which had to be taken care of during the production, is wholly avoided, which makes possible an appreciable increase in the rate of manufacture.
A packing container made from the packing container blank in accordance with the invention has been given the characteristic in accordance with the invention that it includes four wall panels which in pairs have the same outer contours or profiles. Owing to opposite pairs of wall panels being alike a symmetrical packing container is obtained, which rationalizes and simplifies the transport and the steering of the packing container blank through the packing machine as well as the forming of the packing container.
It is a still further object of the present invention to provide a method for manufacturing blanks from a packing material web in the most material-saving manner possible.
This object has been achieved in accordance with the invention in that a method for manufacturing blanks from a packing material web has been given the characteristic in accordance with the invention that the packing material web is cut according to a pattern which at the same time forms a transverse edge of a first blank as well as a transverse edge of a second adjoining blank.
Preferred embodiments of the method in accordance with the invention, moreover, have been given the characteristics which are evident from the description below.
Thanks to the method in accordance with the invention the cutting is facilitated and the design of the cutting elements is simplified, which gives rise to less expensive manufacture and fewer interruptions because of faulty or damaged cutting elements.